[PATCH 3/3] Profile: attempt on better zoom and pan logic
Lubomir I. Ivanov
neolit123 at gmail.com
Thu Jul 4 13:55:27 PDT 2013
From: "Lubomir I. Ivanov" <neolit123 at gmail.com>
QGraphicsView::AnchorUnderMouse does not work for
Qt 4.8.1 on Ubuntu 12.04 and if the mouseMoveEvent
overload is disabled it practically can be seen that
the anchor point is [0, 0] instead of the mouse location.
After a suggestion found on the web this patch attempts
to use the hidden scroll bars to calculate reposition
on pan and zoom *near the mouse cursor.
On the other hand QAbstactSlider (QScrollBar) class
strangly uses negative offsets for minimum scroll
position, which makes the implementation even more
ugly.
[*near] because it's not that accurate!
Signed-off-by: Lubomir I. Ivanov <neolit123 at gmail.com>
---
QGraphicView::translate() is technically a NOP
as there is no way to disable the scene alignment
in Qt 4.8.x. actually, there are bug reports on the
web for that and the recommendation is to add a root
item on the scene (?) and use transformation
matrix on that. centerOn() is another option i didn't try.
there is another bug where if switching views (ctrl+1...n)
the profile zooming becomes broken, but also the text looks
kinda out of position, so i think it's related to another
issue.
please consider testing...
---
qt-ui/profilegraphics.cpp | 29 ++++++++++++++++++++++++-----
qt-ui/profilegraphics.h | 1 +
2 files changed, 25 insertions(+), 5 deletions(-)
diff --git a/qt-ui/profilegraphics.cpp b/qt-ui/profilegraphics.cpp
index cfc1cf6..1cdd2d6 100644
--- a/qt-ui/profilegraphics.cpp
+++ b/qt-ui/profilegraphics.cpp
@@ -6,6 +6,7 @@
#include <QGraphicsScene>
#include <QResizeEvent>
#include <QGraphicsLineItem>
+#include <QScrollBar>
#include <QPen>
#include <QBrush>
#include <QDebug>
@@ -67,12 +68,32 @@ ProfileGraphicsView::ProfileGraphicsView(QWidget* parent) : QGraphicsView(parent
}
+/* since we cannot use translate() directly on the scene we hack on
+ * the scroll bars (hidden) functionality */
+void ProfileGraphicsView::scrollViewTo(const QPoint pos)
+{
+ if (!zoomLevel)
+ return;
+ QScrollBar *vs = verticalScrollBar();
+ QScrollBar *hs = horizontalScrollBar();
+ const qreal yRat = pos.y() / sceneRect().height();
+ const qreal xRat = pos.x() / sceneRect().width();
+ const int vMax = vs->maximum();
+ const int hMax = hs->maximum();
+ const int vMin = vs->minimum();
+ const int hMin = hs->minimum();
+ /* QScrollBar receives crazy negative values for minimum */
+ vs->setValue(yRat * (vMax - vMin) + vMin * 0.9);
+ hs->setValue(xRat * (hMax - hMin) + hMin * 0.9);
+}
+
void ProfileGraphicsView::wheelEvent(QWheelEvent* event)
{
if (!toolTip)
return;
- setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
+ // doesn't seem to work for Qt 4.8.1
+ // setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
// Scale the view / do the zoom
QPoint toolTipPos = mapFromScene(toolTip->pos());
@@ -86,6 +107,7 @@ void ProfileGraphicsView::wheelEvent(QWheelEvent* event)
scale(1.0 / scaleFactor, 1.0 / scaleFactor);
zoomLevel--;
}
+ scrollViewTo(event->pos());
toolTip->setPos(mapToScene(toolTipPos).x(), mapToScene(toolTipPos).y());
}
@@ -98,10 +120,7 @@ void ProfileGraphicsView::mouseMoveEvent(QMouseEvent* event)
QPoint toolTipPos = mapFromScene(toolTip->pos());
- double dx = sceneRect().x();
- double dy = sceneRect().y();
-
- ensureVisible(event->pos().x() + dx, event->pos().y() + dy, 1, 1);
+ scrollViewTo(event->pos());
if (zoomLevel == 0)
QGraphicsView::mouseMoveEvent(event);
diff --git a/qt-ui/profilegraphics.h b/qt-ui/profilegraphics.h
index c3cb4ef..48c88aa 100644
--- a/qt-ui/profilegraphics.h
+++ b/qt-ui/profilegraphics.h
@@ -124,6 +124,7 @@ private:
void plot_depth_scale();
QColor get_sac_color(int sac, int avg_sac);
+ void scrollViewTo(const QPoint pos);
QPen defaultPen;
QBrush defaultBrush;
--
1.7.11.msysgit.0
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